Republican William Weld was governor of Massachusetts from 1991 to 1997. / Cheryl Senter, AP

by Catalina Camia, USA TODAY

by Catalina Camia, USA TODAY

Former Massachusetts governor William Weld said Monday he will not run for the U.S. Senate, as Republicans scramble for a top-tier candidate for the special election to replace John Kerry.

Weld, who served as governor from 1991 to 1997, recently returned to the Bay State after several years in New York City working for private equity and law firms. He is the latest Republican - following former senator Scott Brown and ex-congressional candidate Richard Tisei - to say he would take a pass on the election June 25.

Weld would have been interesting: He endorsed Barack Obama for president in 2008 and was nominated to be ambassador to Mexico by Bill Clinton. Then there's that little matter of running briefly for New York governor in 2006. Weld's decision was reported first by the Associated Press.

Tagg Romney, the eldest son of GOP presidential nominee Mitt Romney, was getting some buzz Monday morning after The Boston Herald reported the younger Romney was "considering a run." ABC News reported that "it's not going to happen," citing two unnamed sources close to both Romneys.

Democratic Reps. Edward Markey and Stephen Lynch have launched their campaigns. The non-partisan Rothenberg Political Report over the weekend changed its rating in the Massachusetts Senate race as "safe Democrat" because of the state's "Democratic bent and the lack of a proven GOP statewide vote-getter."